This is the beginnings of an IMG library intended for use with OSM.

It does not yet work, and is probably the most hideous C++ code you
have ever seen, so unless you are me, I'd advise you go away and come
back later... much later...

All the code is based on the document "Garmin IMG File Format" by John
Mechalas.

The development strategy is roughly:

Phase 1: img2img - a utility that reads in an IMG file, and then
   writes it out again. Smart, huh?

Phase 2: osm2omg - a utility that reads in an OSM file, and then
   writes out an IMG file.

Phase 3: Utilities required to deal with needing different data at
different zoom levels. This may be of generic use for other renderers
too. Also some kind of online interface to allow people to get bang
upto date img for their town/area etc.